A power circuit to achieve power factor correction and method thereof

Abstract

Disclosed herein is a power circuit and a method for achieving power factor correction by controlling the power electronics switches and using a secondary side synchronized rectifier circuit to achieve higher efficiency at a reduced size and cost The power circuit disclosed in the present invention comprises an input source (201) for providing AC input to the circuit, an EMI / EMC section (202) for reducing the conduction emission and radiation in the input, a rectifier section (203) for converting the AC input to DC, a DC-AC section (204) for converting DC to AC, a high-frequency transformer (205) for voltage gain control, a secondary synchronized boost rectifier circuit (206) for achieving power factor correction using multi-mode two-stage operation, an output filter (207) for filtering the output voltage and current ripple and an output load (208) connected to the circuit.

Description

A POWER CIRCUIT TO ACHIEVE POWER FACTOR CORRECTION AND METHOD THEREOFFIELD OF THE INVENTION:

[0001] The present invention generally relates to electrical circuits for achieving power factor correction. More specifically, the present invention relates to a power circuit and a method for achieving power factor correction with higher efficiency while being more compact and cost- effective. A method of operation for the same has been disclosed thereof.BACKGROUND:

[0002] Power electronic circuits play a maj or role in controlling and converting electric power in a circuit. Especially, the power converters are used for converting single-phase alternating current (AC) to isolated direct current (DC). These power converters are used in various applications such as electric vehicle chargers, isolated alternating current to direct current (AC - DC) converters with power factor correction (PFC), battery chargers, power electronic switchingbased welding machines, and industrial loads. In these applications, the power converters or the isolated AC - DC converters are used for power factor correction (PFC).

[0003] A conventional isolated AC-DC converter typically consists of multiple power conversion stages. This converter comprises an alternating current (AC) input source, an Electromagnetic Interference (EMI) / Electromagnetic Compatibility (EMC) section, a full bridge rectifier, a power factor correction (PFC), a DC link capacitor, a direct current to alternating current (DC-AC0 converter, a high-frequency transformer, a secondary rectifier, an output filter and a load connected to the circuit.

[0004] In the conventional isolated AC-DC converter, the PFC section reduces the efficiency as it dissipates more amount of heat during energy conversion. Also, eliminating the PFC leads to a poor power factor at the input and power factor correction must be taken care of by the DC- AC converter. However, if a buck-type converter is used, only a certain portion of the input waveformis controlled. Therefore, PFC plays an important role in the AC - DC converter. So, to achieve a power factor correction, various methods are employed in circuits.

[0005] For example, Chinese Patent Number 107294407 entitled “AC-DC conversion system ” to Zhou Yufei relates to a conversion system for achieving high efficiency and power factor. The AC-DC conversion system disclosed in the patent comprises an input circuit, a rectifier bridge, a buck-boost type PFC main circuit and a resonant-type DC-DC conversion circuit. These components are sequentially connected. The system also comprises a PFC controller, a bus voltage control circuit and a bus voltage sampling circuit. The PFC controller is connected to the buckboost type PFC main circuit. The bus voltage control circuit and the bus voltage sampling circuit are connected to the PFC controller. There is also an input voltage isolation sampling circuit and an output current sampling circuit which are connected to the bus voltage control circuit. A bus voltage reference signal is output by the bus voltage control circuit according to the input voltage and load information.

[0006] Further, United States Patent Number 9621029 entitled “Method and device for high- power-factor flyback converter” to Giovanni Gritti relates to a device for achieving high power factor. The device comprises a switching power converter with a power transistor which is controlled by a controller. The controller includes a multiplier that produces a voltage reference signal. The device also comprises a subtraction circuit, a comparator and a driving circuit. The subtraction circuit subtracts a capacitor signal based on the voltage reference signal, from a sensing signal that is representative of the current flowing through the power transistor. The comparator compares the voltage reference signal to the output of the subtraction circuit, and the driving circuit drives the power transistor based on the comparison resulting in a high-power factor and low total harmonic distortion for the converter.

[0007] Similarly, there are many existing prior art that relate to devices and methods for controlling power factor. However, in the existing devices and methods, power factor correction is achieved by using DC-DC converter with a power factor correction control technique. Moreover, in the existing power factor correction (PFC) circuits, the ripple components that are primarily generated at the input AC are filtered through the input capacitor or input filter providedin the DC link .This technique reduces the efficiency of the isolated AC -DC converter due to switching and conduction losses in the power electronics switches, losses in the diodes, PFC inductors and DC link capacitors, thereby reducing the life of the isolated AC -DC converter . Also, the size of the conventional converter in the existing prior arts is relatively bulky due to the additional power conversion stages and therefore, the cost of the converter is higher.

[0008] Hence, there is a need for a power circuit that achieves power factor correction with high efficiency while being more compact and cost-effective without the need for a dedicated DC- DC converter. The present invention addresses these limitations by providing a power circuit that offers high-efficiency power factor correction in a more compact form factor, eliminating the need for a separate DC-DC converter."OBJECTIVES OF THE INVENTION:

[0009] A primary objective of the present invention is to provide a power circuit to achieve a high efficiency power factor correction using a multi-mode, two-stage operation within a compact and cost-effective power circuit.

[0010] Another objective of the present invention is to provide a power circuit for power factor correction, wherein the AC ripple components generated at the AC input and fed through the circuit is directly transferred to the load.

[0011] Another objective of the present invention is to provide a power circuit for power factor correction without the traditional power factor correction circuit for battery charger application.

[0012] Yet another objective of the present invention is to provide a power circuit that achieves a power factor correction with high efficiency and durability while being more compact and cost-effective.

[0013] Other objects and advantages of the present invention will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the invention.SUMMARY:

[0014] To achieve the aforementioned objectives, the present invention provides a power circuit (i. e. an isolated AC -DC converter) to achieve a power factor correction and a method for achieving power factor correction by controlling the power electronics switches in the DC-AC section and boost type synchronized secondary rectifier section.

[0015] According to the present invention, the power circuit comprises an input source for providing AC input to the circuit, an EMI / EMC section for reducing the conduction emission and radiation in the input, a rectifier section for converting the AC input to variable DC, a DC-AC section for converting a variable DC to AC, a high-frequency transformer for voltage gain , a boost type secondary synchronized rectifier circuit for achieving power factor correction using two - stage operation, an output filter for filtering the output voltage and current ripple and an output load connected to the circuit.

[0016] The present invention encompasses several embodiments, including a second embodiment where the entire power circuit operates on solar power. Additionally, another configuration allows the inductor (312) on the secondary side to be repositioned between the transformer and the MOSFETs, enhancing efficiency and reducing switching losses in the MOSFETs. This adjustment enables the circuit to achieve operational mode 403 without relying on the secondary mode, streamlining its functionality. Furthermore, an additional leg can be added to facilitate operational modes 402 and 403, improving the power factor, albeit with increased costs and a slight efficiency reduction.

[0017] In accordance with the present invention, the method for power factor correction comprises the steps of receiving an input from an AC input source, reducing conduction emissionand radiation in the received input using an EMI / EMC section, converting the AC input to variable DC using a rectifier section, converting DC to AC using a DC-AC section, controlling the voltage gain using a high-frequency transformer, a boost type synchronized secondary rectifier circuit in a multi-mode two stage operation for achieving power factor correction, filtering the output voltage and current ripple using an output filter and receiving the output an output load connected to the circuit.

[0018] Thus, the present invention provides a power circuit without the need for a dedicated traditional boost type power factor correction circuit for power factor correction and taking care of the ripple components thereby achieving higher efficiency while being more compact and cost- effective.

[0019] The arrangement of the present invention has other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following brief description, which together serve to explain certain principles of the present invention.BRIEF DESCRIPTION OF THE DRAWINGS:

[0020] The detailed description is described with reference to the accompanying figures. Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements and features. The features and advantages of the present proposed system will become more apparent from the following detailed description a long with the accompanying figures, which forms a part of this application.

[0021] FIG. 1 depicts a block diagram of a conventional isolated AC-DC conversion module for power factor correction.

[0022] FIG. 2 depicts a block diagram of an isolated AC-DC conversion module according to the present invention.

[0023] FIG. 3 depicts a circuit diagram demonstrating the multimode two stage operation employed in the isolated AC-DC conversion module in accordance with the present invention.

[0024] FIG. 4 depicts a waveform indicating the region of multi-mode two -stage operation for achieving power factor correction in accordance with the present invention.

[0025] FIG. 5 depicts a hardware waveform indicating the input AC voltage (Vac) and input AC current (lac) in accordance with the present invention.

[0026] FIG. 6 shows a hardware waveform indicating the battery voltage (Vbat) and battery current (Ibat) in accordance with the present invention.

[0027] It is to be noted, however, that the appended drawing illustrates only typical embodiments of this system and are therefore should not be considered limiting of its scope, for the system may admit to other equally effective embodiments.REFERENCE NUMERALS:100 - Single Phase AC Input101 - EMI / EMC Section102 - Full Bridge Rectifier Section103 - Power Factor Correction (PFC)104 - DC Link Capacitor105 - DC- AC Converter106 - High Frequency Transformer107 - Secondary Rectifier108 - Output Filter109 - Load201, 301 - Single Phase AC Input202, 302 - EMI / EMC Section203, 319 - Rectifier Section204, 320 - DC- AC Section205, 311 - High Frequency Transformer312 - Transformer206, 320 - Boost type synchronized Secondary Rectifier Circuit207, 317- Output Filter208, 318 - Output Load307, 308, 309, 310, 313, 314, 315, 316- Power Switches317 - Output filter307, 308 - Totem-pole leg 1309, 310 - Totem-pole leg 2313, 314 - Totem-pole leg 3315, 316 - Totem-pole leg 4401 - Incoming AC voltage Vac402 - Mode 1403 - Mode 2DETAILED DESCRIPTION OF THE INVENTION:

[0028] The following is a detailed description of the present disclosure depicted in the accompanying drawings. The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments and drawings in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[0029] If the specification states that a component or a feature “may” or “can” be included, that particular component or feature is not required to be included or have the characteristic. Theuse of open-ended terms like “comprising” and variations herein is meant to encompass the steps listed thereafter and equivalents thereof as well as additional items. As used herein, the singular forms “a,” “an,” and “the” designate both the singular and the plural, unless expressly stated to designate the singular only.

[0030] The term “AC” refers to Alternating current. The term “DC” refers to direct current. The term “PFC” refers to Power Factor Correction. Power Factor Correction, is a technique used in electrical systems to improve the power factor, which is the ratio of real power (watts) to apparent power (volt-amperes) in an AC circuit. Power factor measures how effectively electrical power is being used, and a low power factor indicates poor efficiency, often resulting in wasted energy. The term “EMI” refers to Electromagnetic Interference and the term “EMC” refers to Electromagnetic Compatibility. In power circuits, an EMI / EMC section is used to filter out or suppress unwanted electromagnetic interference, helping the device operate smoothly and without causing issues in other nearby devices. “Ripple” refers to small, unwanted variations or "ripples" in the DC voltage output of a power supply after it has converted AC (alternating current) to DC (direct current). In the context of power electronics, totem-pole legs refer to a specific arrangement of switches in pairs, often used in inverter or rectifier circuits for efficient power conversion. “PWM” refers to Pulse Width Modulation (PWM) which is a technique used to control the amount of power delivered to an electrical load by switching a signal on and off rapidly. “MOSFET” stands for Metal-Oxide-Semiconductor Field-Effect Transistor. It is a type of transistor widely used in electronics to amplify or switch electronic signals. MOSFETs are crucial components in various applications, from power supplies and motor controllers to digital circuits and signal amplifiers.

[0031] The present invention discloses a power circuit and a method for achieving higher efficiency at a reduced size and cost, wherein an embodiment of the present invention utilizes an isolated AC -DC converter.

[0032] According to the present invention, the power circuit comprises an input source for providing AC input to the circuit, an EMI / EMC section for reducing the conduction emission and radiation in the input, a rectifier section for converting the AC input to DC, a DC- AC section forconverting DC to AC, a high-frequency transformer for voltage gain control, a boost type synchronized secondary rectifier circuit for achieving power factor correction using multi-mode two-stage operation, an output filter for filtering the output voltage and current ripple and an output load connected to the circuit.

[0033] In accordance with the present invention, the method for power factor correction comprises the steps of receiving an input from an AC input source, reducing conduction emission and radiation in the received input using an EMI / EMC section, converting the AC input to variable DC using a rectifier section, converting DC to AC using a DC-AC section, controlling the voltage gain using a high-frequency transformer, operating a boost type synchronized secondary rectifier circuit in a multi-mode two-stage operation for achieving power factor correction, filtering the output voltage and current ripple using an output filter and receiving the output an output load connected to the circuit.

[0034] As shown in FIG. 1, the power conversion stages in a traditional / conventional isolated AC-DC converter where AC power is converted to a DC output is illustrated. This converter comprises a single-phase AC input source (100) which obtains the initial AC power input from the mains or another AC source. Next is an EMI / EMC filter section (101) used to suppress electromagnetic interference (EMI) and ensure electromagnetic compatibility (EMC). It removes high-frequency noise and prevents the system from emitting unwanted electromagnetic signals that could interfere with other devices. A full bridge rectifier section (102) is linked to the EMI / EMC filter section (101), wherein the rectifier converts the AC input to an unregulated DC output. A power factor correction (PFC) (103) linked to the rectifier, adjusts the power factor of the system. The DC link capacitor (104) smooths out the DC signal after the rectification and PFC stages. A steady supply of DC is provided to the next stage. A DC-AC converter (105) linked to the capacitor, converts the smoothed DC voltage back into an AC form. A a high-frequency transformer (106) provides electrical isolation between the input and output stages and adjusts the voltage level as required by the load, stepping up or down based on output requirements. A secondary rectifier (107) converts the AC output from the transformer back to DC, wherein an output filter (108) filters out any remaining ripple or noise from the DC signal to provide a smooth, clean DC output for the load. The final DC output is supplied to the connected load (109), whichcould be any device or system requiring conditioned DC power, The final DC output is supplied to the connected load, which could be any device or system requiring conditioned DC power.

[0035] Coming back to FIG. 1, the EMC (101) stage reduces the conduction emission and radiation in the input to meet the standard requirements. The second stage has the full bridge rectifier section (102) which converts the AC input to variable DC. In the third stage, the PFC (103) is performed to maintain the unity power factor. The PFC (103) can be of single boost, interleaved boost converter, totem-pole full bridge, totem-pole half bridge, fly back etc. The purpose of the topology of the PFC (103) is to convert the variable DC to fixed DC and maintain the power factor as unity. The output of the PFC (103) is fed to the DC bus (104) which comprises capacitors to maintain the DC bus voltage as a constant.

[0036] Referring back to FIG. 1, in the fourth stage, the DC-AC conversion is performed using a DC-AC converter (105) which comprises of full bridge or half bridge totem-pole. This bridge converts the DC to high-frequency AC. The MOSFETs or IGBTs in this section are controlled by phase shift Pulse Width Modulation (PWM) to reduce the losses from hard switching. Also, the resonant converter is preferred to reduce the switching losses to a lower level. The output of the DC-AC converter (105) is fed to the high-frequency transformer (106) which is used for the voltage gain control and to provide isolation between the input and output. The secondary of the high-frequency transformer (106) is connected to the secondary rectifier (107). The most commonly used rectifiers are full bridge center tapped or full bridge rectifiers. The final stage is the output filter (108) to reduce the output ripples.

[0037] According to the present invention, the circuit shown in FIG. 2 comprises a singlephase AC input (201), an EMI / EMC section (202), a rectifier section (203), a DC-AC section (204), a high-frequency transformer (205), a boost type synchronized secondary rectifier circuit (206), an output filter (207) and an output load (208) connected to the circuit.

[0038] Referring to FIG.2, the present invention outlines a comprehensive power circuit structure and a method for achieving power factor correction (PFC) within that circuit. The power circuit begins with an input source (AC) (201), where alternating current (AC) power is fed into the system. An EMI / EMC section (202) is integrated, designed to minimize electromagnetic interference (EMI) and ensure electromagnetic compatibility (EMC). Following this, the rectifier section (203) converts the incoming AC power into variable direct current (DC). Afterward, the DC- AC section (204) converts the DC signal back to AC. A high-frequency transformer (205) is utilized in this process to control voltage gain, adjusting the voltage level to meet the output load's requirements while maintaining a compact and efficient design due to its high-frequency operation.

[0039] A crucial component of this circuit is the boost-type synchronized secondary rectifier circuit (206), which implements PFC through a "multi-mode two-stage operation." The output filter (207) then smooths out the AC signal converted to DC, effectively filtering any residual current ripple and noise to ensure a clean and stable DC output for the connected load. Finally, the output load (208) is where the conditioned power is delivered, which could be any device or appliance requiring a regulated power source.

[0040] Further, it is illustrated in in FIG. 2, the power factor correction section (103) is removed and therefore the losses in the section are completely eliminated. Instead, the power factor correction is achieved by switching the power switches (307, 308, 309, 310, 313, 314, 315, and 316) shown in FIG. 3 in a unique pattern. In FIG. 3, the DC- AC converter (320) and the secondary rectifier (321) is employed to achieve power factor correction using a multi-mode two-stage operation (402,403). The output LC filter (314, 315) shown in FIG. 3 is used to filter the output ripples. The switching frequency of all the MOSFETS is controlled to control the magnitude of output current. Therefore, it is understood that the output current ripple components are filtered and reduced at the output filter (207), before transferring the power to the output load (208).

[0041] The two modes of operation for achieving power factor correction are mode 1 (402) and mode 2 (403). According to the present invention, the power circuit operates in a multi-mode two-stage operation to achieve effective power factor correction (PFC). During the operation ofmode 1 (402), the power electronics switches (307, 308, 309, and 310) in the primary side as shown in FIG. 3 are configured to operate using phase shift pulse width modulation (PWM). In this configuration, the phase shift between the totem-pole leg 1 and totem-pole leg 2 is precisely controlled to optimise the power factor correction (PFC). Within this mode (402), the MOSFETS (313, 314, 315, and 316) located in the synchronized secondary side (321) operate in a synchronized rectification mode. This involves the totem-pole leg 3 and totem-pole leg 4 operate at 180-degree phase shift. This means that when one leg is conducting, the other is not, effectively managing the flow of current and reducing losses due to unnecessary switching. Meanwhile totempole leg 1 and totem-pole leg 3 operate at a 0-degree phase shift, allowing for simultaneous conduction. This arrangement not only enhances synchronized rectification but also effectively achieves a marked reduction in output ripple voltage, resulting in a more stable DC output. Additionally, for cost reduction, the MOSFETs (313 , 314) in totem-pole leg 3 can be replaced with diodes, while achieving similar functionality.

[0042] Transitioning to mode 2 (403), the power electronics switches (307, 308, 309, and 310) shown in FIG. 3 continue to utilize phase shift pulse width modulation but now operates at maximum duty cycle. In this mode the phase shift between the totem-pole leg 1 and totem-pole leg 2 is maximized to a 175-degrees instead of the theoretical maximum of 180-degrees. This adjustment facilitates the benefits of zero-voltage switching, reducing switching losses and improving overall efficiency. The power factor correction in this stage is accomplished through the MOSFETS (313, 314, 315, and 316) within the boost type synchronized secondary rectifier circuit (321). The configuration allows these MOSFETs to operate in boost mode, which is critical for stepping up voltage as needed. Furthermore the phase shift between totem pole leg 3 and totem-pole leg 4 is dynamically adjusted by keeping the phase shift between totem-pole leg 1 and totem-pole leg 3 at 0-degree.

[0043] FIG.4 illustrates the waveform indicating the region of multi-mode two stage operation for achieving power factor correction. This figure shows how the power circuit handles the incoming AC voltage (Vac) and converts it to a DC voltage (Vdc) with minimized / reduced ripple. The top waveform labelled (401) represents the incoming AC voltage (Vac), whichalternates in a wave-like pattern over time. The bottom waveform shows the resulting DC voltage (Vdc) after conversion. It has ripples, but they are minimized to keep the output more stable. 402 and 403 represent two different operational modes within the circuit. Mode 402 helps reduce the ripple in the DC output, while Mode 403 further stabilizes it by correcting the power factor. Together, these modes create a smooth, high-quality DC output, which is essential for efficient power usage and minimal energy loss.

[0044] FIG.5 depicts a hardware reading of the input AC voltage (Vac) and input AC current(lac) waveforms in a power circuit. The Vac (Voltage) represents the input AC voltage, which oscillates in a smooth wave-like pattern, coming from a power source. The lac (Current), represents the input AC current waveform, which also oscillates, with variations and some irregularities.

[0045] FIG. 6 illustrates the stable battery voltage (Vbat), which maintains a constant DC level with minimal ripple, indicating effective voltage regulation and filtering. The battery current (Ibat) exhibits a pulsating behaviour at 50 Hz, following a half-wave rectified pattern due to the use of simple half-wave rectification. The battery also serves as a natural filter, smoothing the load.

[0046] Further embodiments of the present invention are as follows. In a second embodiment of the present invention, the entire power circuit can be powered by solar power.

[0047] Yet another embodiment includes that the inductor (312) utilized in the secondary side can be shifted between the transformer and the MOSFETs to improve efficiency, to reducing switching losses in the secondary-side MOSFETs, as depicted in FIG.7. This repositioning allows the circuit to achieve mode 403 without needing to rely on the secondary mode. By optimizing the inductor's placement, the circuit can maintain desired performance characteristics without the complexities introduced by additional modes, streamlining operation. However, this embodiment faces a drawback, wherein this adjustment of shifting the inductor and removal of the boostsynchronized section, can negatively impact the power factor, leading to decreased power quality and efficiency.

[0048] Yet another embodiment of the present invention comprises adding an additional leg to the circuit, facilitating the achievement of both operational modes (402 and 403) with improved power factor, as shown in Fig_8. The additional leg allows the circuit to operate efficiently in both modes, providing flexibility to adapt to different operational requirements with an enhanced power factor. However, this modification does come with trade-offs, including increased costs and a slight reduction in efficiency.

[0049] According to the present invention, the PFC (103) shown in FIG. 1 is eliminated. This improves the efficiency and reduces the size and cost of the electronic power device. The durability of the converter is increased by eliminating the DC link electrolytic capacitors. Further, power factor correction is achieved by the unique control and switching technique of power switches (307, 309, 308, 310, ,313, 314, 315 and 316).

[0050] In one embodiment of the power circuit capable of achieving efficient power factor correction through a versatile rectifier section (203, 319). This section is designed to be configurable as various types of rectifiers, enabling adaptability to meet specific application requirements while optimizing efficiency and performance.

[0051] A full bridge rectifier consists of four diodes arranged to allow current flow during both halves of the AC cycle. This configuration provides full-wave rectification, yielding a higher average output voltage and lower ripple compared to half-wave systems. It is particularly advantageous in high-power applications where efficiency is paramount, making it suitable for industrial and commercial power supplies.

[0052] A half bridge rectifier employs two diodes and is ideal for lower power applications. This design effectively converts AC to DC while simplifying the circuit with fewer components. Although it provides lower output voltage than a full bridge rectifier, its cost-effectiveness and compact design make it suitable for consumer electronics and low-power devices.

[0053] Utilizing a center-tapped transformer, this rectifier allows for efficient full-wave rectification with two diodes. This configuration can deliver higher output voltage and lower ripple compared to half-bridge rectifiers, making it suitable for applications requiring moderate power levels and good voltage regulation.

[0054] A voltage doubler rectifier configuration utilizes capacitors and diodes to effectively double the output voltage from the AC input. This is particularly useful in applications that require a higher DC output without increasing the AC input voltage, optimizing voltage gain and efficiency.

[0055] By replacing conventional diodes with MOSFETs or other controlled switching devices, a synchronous rectifier significantly reduces conduction losses due to its lower on-state resistance. This configuration is essential for high-efficiency power supplies, particularly in applications where switching frequency is high, leading to improved thermal performance and reliability.

[0056] A Schottky rectifiers utilizes Schottky diodes known for their low forward voltage drop and rapid switching capabilities. This configuration is particularly advantageous in high- frequency applications, minimizing power losses and enhancing overall circuit efficiency, making it ideal for switching power supplies and DC-DC converters.

[0057] Active rectifiers utilize actively controlled devices, such as MOSFETs, to improve rectification efficiency. This design dynamically adjusts to minimize losses and optimize performance, making it suitable for advanced power applications where high efficiency and effective power factor correction are critical.

[0058] The flexibility of the rectifier section allows designers to select the appropriate configuration based on application-specific requirements, including power levels, efficiency targets, and performance characteristics. By integrating various rectification methods, the powercircuit can be tailored for optimal operation in diverse environments and load conditions, significantly enhancing its applicability across a wide range of industries.

[0059] The present invention has the following advantages. The multi-mode two-stage operation of the power circuit optimizes power conversion processes, allowing for improved energy transfer with minimal losses. The inclusion of advanced rectification methods, such as synchronous and active rectifiers, significantly reduces conduction losses and enhances overall circuit efficiency. By employing zero-voltage switching techniques, the invention minimizes switching losses, resulting in a system that maintains high performance across various load conditions and improves energy utilization.

[0060] The innovative design of the power circuit eliminates the need for a dedicated traditional boost type power factor correction circuit, thus reducing the overall component count and complexity. By offering a configurable rectifier section that can adapt to various rectifier types — such as full bridge, half bridge, and Schottky rectifiers — manufacturers can tailor the circuit to specific applications without incurring additional costs. This modularity enables cost- effective production and facilitates easier maintenance, leading to reduced lifecycle costs for users.

[0061] The choice of high-quality components and advanced rectification techniques contributes to the long-term reliability and durability of the power circuit. By employing robust devices like MOSFETs in synchronous and active rectifier configurations, the circuit is less susceptible to thermal stress and wear. Additionally, the design minimizes heat generation, which is a primary factor in electronic component degradation, thereby extending the operational lifespan of the system. The circuit's ability to efficiently manage power also reduces the risk of failure, ensuring dependable performance over extended periods.

[0062] The power circuit's architecture, which integrates multiple functionalities into a compact design, results in a significant reduction in physical size and weight. The use of high- frequency transformers and advanced rectification methods allows for miniaturization without compromising performance. This compact design is particularly advantageous in applications withspace constraints, such as portable devices, consumer electronics, and automotive systems. The lightweight nature of the circuit facilitates easier integration into various systems, enhancing portability and reducing installation complexity.

[0063] While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above-described embodiment, method, and examples, but by all embodiments and methods within the scope of the invention as claimed.

Claims

WE CLAIM:

1. A power circuit for achieving power factor correction, wherein the power circuit comprises: a. an input source (201, 301) configured to provide an AC input; b. an EMI / EMC section (202, 302) configured to reduce conduction and radiated emissions in the AC input; c. a rectifier section (203, 319) configured to convert the AC input to a variable DC output; d. a DC-AC section (204, 320) configured to convert the variable DC output to high- frequency AC, while retaining low frequency AC ripple components throughout the circuit; e. a high-frequency transformer (205, 311) configured to control voltage gain; f. a boost-type synchronized secondary rectifier circuit (206, 321) configured to achieve a power factor correction, by operating in a multi-mode, two-stage configuration (402, 403); g. an output filter (207) configured to filter out output voltage and current ripple in the output; and h. an output load (208, 318) connected to the power circuit; wherein the power factor correction is achieved by switching of power switches (307, 308, 309, 310, 313, 314, 315, and 316) arranged in a first totem-pole (307, 308), a second totem-pole (309, 310), a third totem-pole (313, 314), and a fourth totem-pole (315, 316) configuration, the power switches configure to operate across the two modes (402, 403) to enable a reduction of low frequency ripple component from the AC input to flow to the load (208, 318).

2. The power circuit as claimed in claim 1 wherein the power switches on totem-pole legs 1 and 2 comprise of power electronic switches on a primary side.

3. The power circuit as claimed in claim 1 wherein the power switches on totem-pole legs 3 and 4 comprise of MOSFETS on a secondary side.

4. The power circuit as claimed in claim 1 wherein the power switches on totem-pole legs 3 comprise of diodes.

5. The power circuit as claimed in claim 1, wherein the boost-type synchronized secondary rectifier circuit is configured to adjust the phase of the power switches dynamically to align current and voltage waveforms, thus providing the power factor correction.

6. The power circuit as claimed in claim 1, wherein the mode 1 (402) includes: the DC-AC section (320) configured to operate utilizing a phase-shift pulse width modulation (PWM) with a controlled phase shift between the first totem-pole leg and the second totem-pole leg to achieve said power factor correction; and the synchronized secondary rectifier circuit (321) is configured to operate in a synchronized rectification mode, wherein at least the third totem-pole and fourth totem-pole legs are configured to operate with a phase shift of at least 180-degrees.

7. The power circuit as claimed in claim 1, wherein in Mode 1 (402) the phase shift between the third and fourth totem-pole legs is dynamically controlled by maintaining a 0-degree phase shift between the first totem-pole leg and the third totem-pole leg.

8. The power circuit as claimed in Claim 1, wherein in Mode 2 (403), the power switches configured to operate with phase shift pulse-width modulation (PWM), including: the first and second totem-pole leg, wherein each leg includes two power electronics switches and operates in phase-shift PWM at a maximized duty cycle, and the third and fourth totem-pole leg configured to adjust phase dynamically relative to the first and second legs,9. The power circuit as claimed in claim 1, where in Mode 2 (403): the synchronized secondary rectifier circuit (321) is configured to operate in a boost mode to achieve power factor correction and further reduce AC ripple components; and the DC- AC section (320) is configured to operate in phase-shift pulse width modulation (PWM) at a maximum duty cycle, with a phase shift between the first and second totem-pole legs to 175 degrees, set to enable zero-voltage switching.

10. The power circuit as claimed in claim 1, wherein the rectifier section (203, 319) is configurable as a full bridge rectifier, half bridge rectifier, center-tapped full-wave rectifier, voltage doubler rectifier, synchronous rectifier, Schottky rectifier, or active rectifier, allowing for flexibility in design to optimize efficiency, performance, and power factor correction based on application requirements.

11. The power circuit as claimed in claim 1, wherein the power circuit is powered by solar power.

12. The power circuit as claimed in claim 1, wherein the inductor (312) utilized on the secondary side is repositionable between the transformer and the MOSFETs, enabling the circuit to achieve the mode (403) without reliance on the secondary mode.

13. The power circuit as claimed in claim 1, comprising an additional leg that facilitates the achievement of both operational modes (402 and 403) with an enhanced power factor.

14. A method for achieving power factor correction in a power circuit, the method comprising: receiving a single-phase AC input at an input terminal; reducing conduction and radiative emissions from the AC input using an EMI / EMC filter; converting the AC input to DC using a rectifier stage; converting the DC output from the rectifier to a high-frequency AC using a DC- AC converter;regulating voltage gain through a high-frequency transformer; correcting the power factor through a boost-type synchronized secondary rectifier circuit operating in multiple modes (402, 403), including: a. a first mode (402), wherein power switches are controlled in a first switching pattern to initiate power factor correction, and b. a second mode (403), wherein the power switches are controlled in a second switching pattern to further optimize power factor correction; filtering output voltage and current ripple with an output filter; and supplying the filtered output to an output load.

15. The method as claimed in claim 14, wherein the second mode (403) of operation in the boosttype synchronized secondary rectifier circuit includes adjusting the duty cycle of the power switches to a maximum value to further enhance power factor correction.

16. The method as claimed in claim 14, further comprising dynamically adjusting the phase shift between the power switches in the first and second modes of operation to reduce switching losses and achieve zero-voltage switching.

17. The method as claimed in claim 14, wherein the high-frequency AC generated by the DC- AC converter has a frequency optimized for minimal transformer losses during voltage gain adjustment.

18. The method as claimed in claim 14, further comprising the step of synchronizing the switching patterns of the power switches in the boost-type synchronized secondary rectifier circuit to maintain alignment between current and voltage waveforms for enhanced power factor correction.

19. The method as claimed in claim 14, wherein the output filter is configured to suppress both voltage and current ripple in the output signal.

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